2-Chloro-5-trichloromethylpyridine (β-2-tet) is a key intermediate for the production of several agricultural chemicals including, for example, fluazifop, haloxyfop, fluazuron and fluazinam. However, β-2-tet is difficult to obtain by direct chlorination of β-picoline. U.S. Pat. Nos. 3,370,062 and 3,420,833 describe the uncatalyzed vapor phase chlorination of picolines in general. The uncatalyzed vapor phase chlorination of β-picoline is described in U.S. Pat. Nos. 4,205,175, 4,241,213 and 5,247,093. U.S. Pat. No. 4,288,599 describes the the sequential chlorination and fluorination of β-picoline in the vapor phase. U.S. Pat. No. 4,429,132 describes the vapor phase chlorination of β-picoline in the presence of a metal oxide or a metal halide catalyst. The uncatalyzed liquid phase chlorination of β-picoline is described in U.S. Pat. Nos. 4,483,993 and 4,497,955 and the ultraviolet catalyzed liquid phase chlorination of β-picoline is described in U.S. Pat. No. 4,324,627. However, none of these processes provide β-2-tet in good yield at high conversion of β-picoline.
Because of the difficulty in obtaining β-2-tet by direct chlorination of β-picoline, it would be desirable to have a direct chlorination process with improved selectivity to β-2-tet.